Samarao, Ashwin Kumar.
Compensation and trimming for silicon micromechanical resonators and resonator arrays for timing and spectral processing.
Degree: PhD, Electrical and Computer Engineering, 2011, Georgia Tech
This dissertation reports very novel solutions for the trimming and compensation of various parameters of silicon micromechanical resonators and resonator-arrays. Post-fabrication trimming of resonance frequency to a target value is facilitated by diffusing in a deposited thin metal layer into a Joule-heated silicon resonator. Up to ~400 kHz of trimming-up and trimming-down in a 100 MHz Silicon Bulk Acoustic Resonators (SiBARs) are demonstrated via gold and aluminum diffusion respectively. The dependence of the trimming range on the duration of Joule heating and value of current passed are presented and the possibility of extending the trimming range up to ~4 MHz is demonstrated. Passive temperature compensation techniques are developed to drastically reduce the temperature coefficient of frequency (TCF) of silicon resonators. The dependence of TCF on the charge carriers in silicon are extensively studied and exploited for the very first time to achieve temperature compensation. A charge surplus via degenerate doping using boron and aluminum is shown to reduce a starting TCF of -30 ppm/°C to -1.5 ppm/°C while a charge depletion effected by creating multiple pn-junctions reduces the TCF to -3 ppm/°C. Further, shear acoustic waves in silicon microresonators have also been identified to effect a TCF reduction and have been excited in a concave SiBAR (or CBAR) to exhibit a TCF that is 15 ppm/°C lesser than that of a conventional rectangular SiBAR. The study on quality factor (Q) sensitivity to the various crystallographic axis of transduction in silicon resonators show that the non-repeatability of Q across various fabrication batches are due to the minor angular misalignment of ≤ 0.5° during the photolithography processes. Preferred axes of transduction for minimal misalignment sensitivity are identified and novel low-loss resonator-array type performances are also reported from a single resonator while transduced along certain specific crystallographic axes. Details are presented on an unprecedented new technique to create and fill charge traps on the silicon resonator which allows the operation of the capacitive SiBARs without the application of any polarization voltages (Vp) for the first time, making them very attractive candidates for ultra-low-power oscillator and sensor applications. Finally, a fabrication process that integrates both the capacitive and piezoelectric actuation/sensing schemes in microresonators is developed and is shown to compensate for the parasitics in capacitive silicon resonators while maintaining their high-Q.
Advisors/Committee Members: Ayazi, Farrokh (Committee Chair), Allen, Mark (Committee Member), Brand, Oliver (Committee Member), Garmestani, Hamid (Committee Member), Ghovanloo, Maysam (Committee Member).
Subjects/Keywords: AlN-HARPSS; Combined capacitive and piezoelectric; Quality factor sensitivity; Temperature compensation; TCF compensation; Electrical trimming; TCF; Capacitive silicon microresonators; Silicon resonators; Silicon microresonators; Silicon micromechanical resonators; Piezoelectric silicon microresonators; Self polarized; Charge trap; Zero-Vp; HARPSS; Microelectromechanical systems; Resonators; Silicon
7.2.1 Zero-Vp Zero-TCF Silicon Resonator Platforms
7.2.2 High-performance M… …Simulated WEM the SiBAR used to demonstrate zero-Vp
operation. (W = 40 µm; L = 6 × W = 240 µm… …externally applied Vp.
Figure 77: Measured Zero-Vp response from a SiBAR in air at varying… …100
factors of 33 un-encapsulated SiBARs at zero-Vp.
Figure 82: Schematic illustrating the… …the Vp
is ramped up from 0 V to 16 V. Filling of charge traps in this work is
to Zotero / EndNote / Reference
APA (6th Edition):
Samarao, A. K. (2011). Compensation and trimming for silicon micromechanical resonators and resonator arrays for timing and spectral processing. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/39543
Chicago Manual of Style (16th Edition):
Samarao, Ashwin Kumar. “Compensation and trimming for silicon micromechanical resonators and resonator arrays for timing and spectral processing.” 2011. Doctoral Dissertation, Georgia Tech. Accessed October 23, 2019.
MLA Handbook (7th Edition):
Samarao, Ashwin Kumar. “Compensation and trimming for silicon micromechanical resonators and resonator arrays for timing and spectral processing.” 2011. Web. 23 Oct 2019.
Samarao AK. Compensation and trimming for silicon micromechanical resonators and resonator arrays for timing and spectral processing. [Internet] [Doctoral dissertation]. Georgia Tech; 2011. [cited 2019 Oct 23].
Available from: http://hdl.handle.net/1853/39543.
Council of Science Editors:
Samarao AK. Compensation and trimming for silicon micromechanical resonators and resonator arrays for timing and spectral processing. [Doctoral Dissertation]. Georgia Tech; 2011. Available from: http://hdl.handle.net/1853/39543